Description

RPC library routines allow C language programs to make procedure calls
on other machines across the network. First a CLIENT handle is created
and then the client calls a procedure to send a request to
the server. On receipt of the request, the server calls a dispatch routine
to perform the requested service, and then sends a reply.

These routines are MT-Safe. In the case of multithreaded applications, the -mt
option must be specified on the command line at compilation time. When
the -mt option is specified, rpc_createerr() becomes a macro that enables each
thread to have its own rpc_createerr(). See threads(5).

Routines

A function macro to change or retrieve various information about a client object. req indicates the type of operation, and info is a pointer to the information. For both connectionless and connection-oriented transports, the supported values of req and their argument types and what they do are:

If the timeout is set using clnt_control(), the timeout argument passed by clnt_call() is ignored in all subsequent calls. If the timeout value is set to 0, clnt_control() immediately returns RPC_TIMEDOUT. Set the timeout parameter to 0 for batching calls.

CLGET_SERVER_ADDR struct netbuf * get server's address
CLGET_SVC_ADDR struct netbuf * get server's address
CLGET_FD int * get associated file descriptor
CLSET_FD_CLOSE void close the file descriptor when
destroying the client handle
(see clnt_destroy())
CLSET_FD_NCLOSE void do not close the file
descriptor when destroying the client handle
CLGET_VERS rpcvers_t get the RPC program's version
number associated with the
client handle
CLSET_VERS rpcvers_t set the RPC program's version
number associated with the
client handle. This assumes
that the RPC server for this
new version is still listening
at the address of the previous
version.
CLGET_XID uint32_t get the XID of the previous
remote procedure call
CLSET_XID uint32_t set the XID of the next
remote procedure call
CLGET_PROG rpcprog_t get program number
CLSET_PROG rpcprog_t set program number

The following operations are valid for connection-oriented transports only:

CLSET_IO_MODE rpciomode_t* set the IO mode used
to send one-way requests. The argument for this operation
can be either:
- RPC_CL_BLOCKING all sending operations block
until the underlying transport protocol has
accepted requests. If you specify this argument
you cannot use flush and getting and setting buffer
size is meaningless.
- RPC_CL_NONBLOCKING sending operations do not
block and return as soon as requests enter the buffer.
You can now use non-blocking I/O. The requests in the
buffer are pending. The requests are sent to
the server as soon as a two-way request is sent
or a flush is done. You are responsible for flushing
the buffer. When you choose RPC_CL_NONBLOCKING argument
you have a choice of flush modes as specified by
CLSET_FLUSH_MODE.
CLGET_IO_MODE rpciomode_t* get the current IO mode
CLSET_FLUSH_MODE rpcflushmode_t* set the flush mode.
The flush mode can only be used in non-blocking I/O mode.
The argument can be either of the following:
- RPC_CL_BESTEFFORT_FLUSH: All flushes send requests
in the buffer until the transport end-point blocks.
If the transport connection is congested, the call
returns directly.
- RPC_CL_BLOCKING_FLUSH: Flush blocks until the
underlying transport protocol accepts all pending
requests into the queue.
CLGET_FLUSH_MODE rpcflushmode_t* get the current flush mode.
CLFLUSH rpcflushmode_t flush the pending requests.
This command can only be used in non-blocking I/O mode.
The flush policy depends on which of the following
parameters is specified:
- RPC_CL_DEFAULT_FLUSH, or NULL: The flush is done
according to the current flush mode policy
(see CLSET_FLUSH_MODE option).
- RPC_CL_BESTEFFORT_FLUSH: The flush tries
to send pending requests without blocking; the call
returns directly. If the transport connection is
congested, this call could return without the request
being sent.
- RPC_CL_BLOCKING_FLUSH: The flush sends all pending
requests. This call will block until all the requests
have been accepted by the transport layer.
CLSET_CONNMAXREC_SIZE int* set the buffer size.
It is not possible to dynamically
resize the buffer if it contains data.
The default size of the buffer is 16 kilobytes.
CLGET_CONNMAXREC_SIZE int* get the current size of the
buffer
CLGET_CURRENT_REC_SIZE int* get the size of
the pending requests stored in the buffer. Use of this
command is only recommended when you are in non-blocking
I/O mode. The current size of the buffer is always zero
when the handle is in blocking mode as the buffer is not
used in this mode.

The following operations are valid for connectionless transports only:

The retry timeout is the time that RPC waits for the server to reply before retransmitting the request.

clnt_control() returns TRUE on success and FALSE on failure.

clnt_create()

Generic client creation routine for program prognum and version versnum. host identifies the name of the remote host where the server is located. nettype indicates the class of transport protocol to use. The transports are tried in left to right order in NETPATH variable or in top to bottom order in the netconfig database.

clnt_create() tries all the transports of the nettype class available from the NETPATH environment variable and the netconfig database, and chooses the first successful one. A default timeout is set and can be modified using clnt_control(). This routine returns NULL if it fails. The clnt_pcreateerror() routine can be used to print the reason for failure.

Note that clnt_create() returns a valid client handle even if the particular version number supplied to clnt_create() is not registered with the rpcbind service. This mismatch will be discovered by a clnt_call later (see rpc_clnt_calls(3NSL)).

clnt_create_timed()

Generic client creation routine which is similar to clnt_create() but which also has the additional parameter timeout that specifies the maximum amount of time allowed for each transport class tried. In all other respects, the clnt_create_timed() call behaves exactly like the clnt_create() call.

clnt_create_vers()

Generic client creation routine which is similar to clnt_create() but which also checks for the version availability. host identifies the name of the remote host where the server is located. nettype indicates the class transport protocols to be used. If the routine is successful it returns a client handle created for the highest version between vers_low and vers_high that is supported by the server. vers_outp is set to this value. That is, after a successful return vers_low <= *vers_outp <= vers_high. If no version between vers_low and vers_high is supported by the server then the routine fails and returns NULL. A default timeout is set and can be modified using clnt_control(). This routine returns NULL if it fails. The clnt_pcreateerror() routine can be used to print the reason for failure.

Note: clnt_create() returns a valid client handle even if the particular version number supplied to clnt_create() is not registered with the rpcbind service. This mismatch will be discovered by a clnt_call later (see rpc_clnt_calls(3NSL)). However, clnt_create_vers() does this for you and returns a valid handle only if a version within the range supplied is supported by the server.

clnt_create_vers_timed()

Generic client creation routine similar to clnt_create_vers() but with the additional parameter timeout, which specifies the maximum amount of time allowed for each transport class tried. In all other respects, the clnt_create_vers_timed() call behaves exactly like the clnt_create_vers() call.

clnt_destroy()

A function macro that destroys the client's RPC handle. Destruction usually involves deallocation of private data structures, including clnt itself. Use of clnt is undefined after calling clnt_destroy(). If the RPC library opened the associated file descriptor, or CLSET_FD_CLOSE was set using clnt_control(), the file descriptor will be closed.

This routine creates an RPC client for the remote program prognum and version versnum; the client uses a connectionless transport. The remote program is located at address svcaddr. The parameter fildes is an open and bound file descriptor. This routine will resend the call message in intervals of 15 seconds until a response is received or until the call times out. The total time for the call to time out is specified by clnt_call() (see clnt_call() in rpc_clnt_calls(3NSL)). The retry time out and the total time out periods can be changed using clnt_control(). The user may set the size of the send and receive buffers with the parameters sendsz and recvsz; values of 0 choose suitable defaults. This routine returns NULL if it fails.

clnt_pcreateerror()

Print a message to standard error indicating why a client RPC handle could not be created. The message is prepended with the string s and a colon, and appended with a newline.

clnt_raw_create()

This routine creates an RPC client handle for the remote program prognum and version versnum. The transport used to pass messages to the service is a buffer within the process's address space, so the corresponding RPC server should live in the same address space; (see svc_raw_create() in rpc_svc_create(3NSL)). This allows simulation of RPC and measurement of RPC overheads, such as round trip times, without any kernel or networking interference. This routine returns NULL if it fails. clnt_raw_create() should be called after svc_raw_create().

clnt_spcreateerror()

Like clnt_pcreateerror(), except that it returns a string instead of printing to the standard error. A newline is not appended to the message in this case.

Warning: returns a pointer to a buffer that is overwritten on each call. In multithread applications, this buffer is implemented as thread-specific data.

clnt_tli_create()

This routine creates an RPC client handle for the remote program prognum and version versnum. The remote program is located at address svcaddr. If svcaddr is NULL and it is connection-oriented, it is assumed that the file descriptor is connected. For connectionless transports, if svcaddr is NULL, RPC_UNKNOWNADDR error is set. fildes is a file descriptor which may be open, bound and connected. If it is RPC_ANYFD, it opens a file descriptor on the transport specified by netconf. If fildes is RPC_ANYFD and netconf is NULL, a RPC_UNKNOWNPROTO error is set. If fildes is unbound, then it will attempt to bind the descriptor. The user may specify the size of the buffers with the parameters sendsz and recvsz; values of 0 choose suitable defaults. Depending upon the type of the transport (connection-oriented or connectionless), clnt_tli_create() calls appropriate client creation routines. This routine returns NULL if it fails. The clnt_pcreateerror() routine can be used to print the reason for failure. The remote rpcbind service (see rpcbind(1M)) is not consulted for the address of the remote service.

clnt_tp_create()

Like clnt_create() except clnt_tp_create() tries only one transport specified through netconf.

clnt_tp_create() creates a client handle for the program prognum, the version versnum, and for the transport specified by netconf. Default options are set, which can be changed using clnt_control() calls. The remote rpcbind service on the host host is consulted for the address of the remote service. This routine returns NULL if it fails. The clnt_pcreateerror() routine can be used to print the reason for failure.

clnt_tp_create_timed()

Like clnt_tp_create() except clnt_tp_create_timed() has the extra parameter timeout which specifies the maximum time allowed for the creation attempt to succeed. In all other respects, the clnt_tp_create_timed() call behaves exactly like the clnt_tp_create() call.

clnt_vc_create()

This routine creates an RPC client for the remote program prognum and version versnum; the client uses a connection-oriented transport. The remote program is located at address svcaddr. The parameter fildes is an open and bound file descriptor. The user may specify the size of the send and receive buffers with the parameters sendsz and recvsz; values of 0 choose suitable defaults. This routine returns NULL if it fails.

The address svcaddr should not be NULL and should point to the actual address of the remote program. clnt_vc_create() does not consult the remote rpcbind service for this information.

rpc_createerr()

A global variable whose value is set by any RPC client handle creation routine that fails. It is used by the routine clnt_pcreateerror() to print the reason for the failure.

In multithreaded applications, rpc_createerr becomes a macro which enables each thread to have its own rpc_createerr.

clnt_door_create()

This routine creates an RPC client handle over doors for the given program prognum and version versnum. Doors is a transport mechanism that facilitates fast data transfer between processes on the same machine. The user may set the size of the send buffer with the parameter sendsz. If sendsz is 0, the corresponding default buffer size is 16 Kbyte. The clnt_door_create() routine returns NULL if it fails and sets a value for rpc_createerr.